Abstract
College students use substances for varied reasons, including to cope with stress. The parasympathetic nervous system (PNS) regulates bodily functions to promote energy conservation (the 'rest and digest' response), and individuals differ in their physiological sensitivity to challenge. It remains unclear whether greater PNS responses (i.e., declines in PNS activity, termed vagal withdrawal) to challenge could suggest difficulty regulating and thereby confer risk for using substances in community samples. We hypothesised that lower resting PNS activity and greater PNS responses to a challenge task would be associated with more frequent substance use (i.e., alcohol use, binge drinking, cannabis use). College students (N = 152; Mage = 20.5, SD = 3.2; 73.8% female) reported their past month frequency of substance use and completed a laboratory-based challenge task while having an electrocardiogram administered to derive respiratory sinus arrhythmia (RSA), a measure of PNS activity. They watched a 4-min neutral video (resting baseline) and then traced a star with their nondominant hand while only seeing the mirror reflection of their hand (challenge). Higher resting RSA was related to more frequent cannabis use. Individuals with larger declines in RSA from the video to the task (i.e., greater PNS responses) tended to use each substance more frequently. RSA recovery from the task was not related to substance use. Taken together, college students who are more physiologically responsive to challenge may use substances more frequently, potentially as a means of coping. Biofeedback interventions can be investigated for reducing college students' substance use risk.